In industrial inspection, it is often important to measure the roughness of a manufactured surface, or the presence of defects such as cracks, pits, or gouges. There are instruments commercially available for surface metrology, including diamond scribe profilometers and non-contact optical profilometers. However, these devices have various limitations in terms of their expense, their portability, their accuracy, and the speed at which they provide measurements.
There are also various methods for getting 3D surface data by optical means, including structured light, depth from defocus, photometric stereo, and multiview stereopsis. However, these techniques work best on materials that are matte and opaque. Specular, translucent, or transparent materials are more difficult for these techniques, and many of the materials of greatest interest are in these categories.
One domain of particular importance for detailed topography is skin profilometry. Skin has both translucency and specularity, making its topography difficult to measure by standard optical means. Dermatologists, cosmetic surgeons, cosmetic manufacturers, and cosmetic consumers, are often interested in measuring the topography of the skin. For example, topography is measured before and after a wrinkle reduction treatment to quantify the treatment's efficacy. Due to the optical challenges, a popular method of measuring skin topography is to make a silicone replica of the skin and then to perform profilometry on the replica. This is slow and inconvenient. There are also specialized optical skin profilometers designed to overcome the optical challenges posed by human skin, from such companies as GFMesstechnik of Germany (e.g., the PRIMOS), and Courage-Khazaka of Germany (e.g., the Visiometer). These devices tend to be expensive and slow due to the hardware and software that are required to overcome the fact that skin is neither matte nor opaque.
Thus, there is a need to examine and measure the detailed topography of various surfaces inexpensively, quickly, and accurately.